Leak-proof drinking devices have generally been known particularly for infants and sports, which usually have a body and a lid or cap closing the body. In the typical construction, for example as disclosed in UK Patent No. 2266045, the lid has an outlet for liquid and an air inlet for pressure balance, each of which is fitted with a normally-closed one-way valve to avoid leakage.
In general, some of the known devices incorporate relatively complicated mechanisms with small parts and, on occasion, metal springs, which are expensive and not easy to clean. Most of the other designs make use of a thin membrane at the base of a protruding mouthpiece, which includes a slit or opening to provide a passage for liquid and, while the opening is closed, to prevent leakage of liquid. In case of vigorous liquid movement inside the cup (e.g., shaking or dropping), liquid can easily leak out upon directly hitting the slit or the membrane. Liquid flow rate is usually inadequate, as it is often compromised by the leak-proof requirement. None of the known devices is found to be satisfactory in one or more of these areas.
The invention seeks to mitigate or at least alleviate at least some of these drawbacks by providing an improved closure assembly.